Diabetes is a near-pandemic disease with substantial morbidity associated with non-healing foot ulcers (DFUs). Impaired angiogenesis is a limiting factor for wound healing in diabetics, and thus therapeutic vascularization approaches have been applied to treat DFUs. However, cell-based therapeutic vascularization has yet to be validated in large clinical trials and conventional drug and protein treatments have largely failed or been disappointing. Therefore, the development of improved therapeutic vascularization approaches to treat DFUs would fill a critical clinical need. One emerging strategy for molecular therapeutic vascularization is engagement of the ErbB receptor family with Neuregulin-1 (NRG). Though well studied in cancer and many organ systems, relatively little is known about the role of NRG/ErbB signaling in vascularization. NRG is a known endothelial cell mitogen and has been shown to be a crucial mediator of the angiogenic response to ischemia in a mouse model. NRG splice variants, as well as other proteins in the NRG subfamily, are also potential endothelial effectors via their high binding affinity to receptors ErbB3 and ErbB4. Overwhelming evidence indicates that ErbB receptors initiate signaling following dimerization, most often with another ErbB family member. Given that there are four known ErbB receptors, one of which (ErbB2) does not have a known ligand and is thought to exist in a quasi-activated state, splice variants of NRG are capable of inducing signaling through multiple ErbB dimers or oligomers, each set of which may activate a unique pathway. Thus, the role of NRG/ErbB signaling in vascularization is unclear and the potential to maximize the efficacy of ErbB ligands in therapeutic vascularization remains unrealized. In this application, the role of ErbB receptors in vascularization will be explored by pursuing three specific aims. Aim 1 will test the hypothesis that biasing of endothelial ErbB signaling can regulate endothelial cell phenotype. Experiments in Aim 2 will test the hypothesis that local delivery of ErbB receptor ligands can stimulate therapeutic vascularization in vivo via an endothelial ErbB receptor-mediated mechanism. In Aim 3, the hypothesis that skin substitute engraftment can be enhanced via integration with local delivery of ErbB receptor ligands will be tested. At the conclusion of this work, significant steps towards clarifying the role of ErbB receptors in vascularization and determining their potential as therapeutic targets in diabetic wound healing will have been taken. Furthermore, this project has broader implications; the therapeutic strategies developed here have the potential to serve as an enabling technology in the field of tissue engineering. Relevance to Public Health - Therapeutic vascularization via engagement of ErbB receptors is a novel, promising approach to decreasing morbidity and mortality associated with non-healing diabetic foot ulcers. Here, the use of new technology and strategies to develop an improved mechanistic understanding of ErbB receptors in vascularization is proposed. This advances would enable new therapeutic approaches in diabetic wound healing.